The four marks or characteristics of the Church as listed in the Nicene Creed are One, Holy, Catholic, and Apostolic. Saint Robert Bellarmine (1542–1621) expanded these into fifteen marks, but the Creed still only mentions those four. They denote characteristics of the true Church, that is, the one founded by Christ Himself. Think of them as trademarks that identify the maker of the product.
Unity is the first mark of the Church as expressed in the Creed by the words “I believe in one…Church.” When there is unity, there is harmony. The human body is one whole, and the whole is greater than the sum of the parts. We have two lungs, two eyes, five senses, many bones and organs—but it is one whole body. The image and analogy of the body being one yet having many parts with different functions is used by Saint Paul to describe the Church in Romans 12:4–5: “For as in one body we have many parts, and all the parts do not have the same function, so we, though many, are one body in Christ.”
The Church has one set of doctrines (Catechism), one unified standard of public worship (Seven Sacraments) and one set of universal rules and regulations (Code of Canon Law). There is one visible head of the Church, the pope, who is simultaneously the bishop of Rome. He is given the title of Vicar of Christ and Successor of Saint Peter, who is considered the first pope of the Church (Matthew 16:18). The Catholic Church in the United States teaches the same doctrines and celebrates the same sacraments as the Catholic Church in Great Britain, Ireland, Italy, Spain, Portugal, Germany, Mexico, Canada, Poland, France, and all over the world. Unity of content of faith (doctrinal and moral teachings), unity of structure (one connected and integrated hierarchy with the pope as supreme head), and unity of worship (the same seven sacraments all over the world) are components of the true Church. This unity does not, however, destroy or oppose diversity. While there is one set of doctrines and discipline, there are many flavors and expressions of faith as we will see in the third mark.
Sanctity, or holiness, is the second mark of the Church as expressed in the words “I believe in one holy…Church.” Since the founder is Jesus Christ, and He is the Son of God and the Second Person of the Holy Trinity, and Jesus said He would build His Church (Matthew 16:18), the Church herself must be holy due to her divine origins. The Church is the Mystical Body of Christ (Romans 12:4–5), and she is also the spotless bride (spouse) of Christ (Ephesians 5:25; Revelation or Apocalypse 21:2). Jesus entrusted to the Church the Seven Sacraments, which He Himself instituted. It is through the sacraments that men and women are sanctified and made holy by the divine grace they communicate.
Universality is the second mark of the Church as expressed in the words “I believe in one, holy, Catholic…Church.” The diversity of the Church is embodied in the notion that the Church is truly universal (katholikos in Greek). This means it is not a national church, like the Church of England or the Church of Scotland. Unlike the Greek Orthodox or the Russian Orthodox Churches, no one nationality or culture exclusively identifies the Church. There is an Eastern (Byzantine) and a Western (Latin or Roman) part of the Catholic Church, yet they all recognize the same leader (the pope) and the same creed (Catechism). Though the head of the Church is the bishop of Rome, he is assisted by cardinals from around the world. Every country has one or more cardinals who advise the pope and who elect a new pope when the old one dies. All of them are also eligible to be elected pope, no matter what their race, language, or nationality. There are several Eastern liturgical traditions in the Church—Ruthenian, Ukrainian, Maronite, Melkite, Coptic, and Ethiopian, to name a few—and in the West there is the Novus Ordo of Paul VI (the present day Liturgy in the vernacular since Vatican II) and the Tridentine Mass of Pius V (the old Latin Mass since the Council of Trent). Whether Latin or English, Greek or Old Slavonic, Roman or Eastern, the substantial elements of the Mass (Divine Liturgy) are the same. Bread and wine are considered changed into the real, true, and substantial Body and Blood, Soul and Divinity of Christ by the validly ordained priest saying the exact words of Christ (called the Consecration).
Apostolicity is the fourth mark of the Church as expressed in the words “I believe in one, holy, Catholic and apostolic Church.” This term means the religion can trace itself back to the original twelve apostles. Built on the foundation of the apostles (Ephesians 2:20; John 6:70) and continued in their successors, the bishops, the Church exists two millennia later, yet always with a firm connection to its roots. Every bishop who is ordained must be ordained by a bishop who can trace his “lineage of Holy Orders” back to one of the original twelve apostles. This is called Apostolic Succession. Just as Pope Benedict XVI is the 265th successor to Saint Peter, each Catholic bishop is a successor to the apostles. This scrupulous historical connection to the original apostles is not mere nostalgia. Saint Vincent of Lerins (fifth century AD) said it ensured the continuity of faith so that only orthodox teaching would be preserved. Apostolicity ensures that that which is taught everywhere, at all times, in all places (quod ubique, quod semper, quod ab omnibus) is sound doctrine.
Saint Augustine (fourth century AD) said, “There are many other things which most properly can keep me in (the Catholic Church’s) bosom. The unanimity of peoples and nations keeps me here. Her authority, inaugurated in miracles, nourished by hope, augmented by love, and confirmed by her age, keeps me here. The succession of priests, from the very see of the apostle Peter, to whom the Lord, after his resurrection, gave the charge of feeding his sheep (John 21:15–17), up to the present episcopate, keeps me here. And last, the very name Catholic, which, not without reason, belongs to this Church alone.”